The cataract condition is a well known eye ailment, which these days is easily treatable through surgery. The condition involves an opacification, yellowing or clouding of the natural crystalline lens (see FIG. 1), which is situated just behind the iris and serves to focus the incoming image onto the retina at the back of the eye.
The surgical procedure involves the removal of the opaque lens and its substitution by an artificial lens having the required focusing effect.
One way of achieving this is described in U.S. Pat. No. 3,925,825. FIGS. 2 and 3 correspond to FIGS. 1 and 2 of this patent, and show the placing of a lens 10 anterior to the iris 12. The lens is held in place against the iris by a haptic section 14. The haptic section 14 consists of a series of bent wire loops 16, which are attached to a circular wire frame 18. The lens 10 has a flat circumferential face 20 and the lens is held within the frame 18 by inserting the lens inside the frame 18 and closing the legs 22 of the frame so that the frame 18 closes tightly against the lens face 20. Once the legs 22 have been brought together, their ends are kept together via a terminal part 24.
One way of extracting the opaque natural lens—a process known as extra-capsular extraction—will now be described. Reference is first made to US 2003/0130732, FIG. 1 of which corresponds to FIG. 4 of the present application. The lens 30 is accommodated within a so-called capsule (also sometimes referred to as a “capsular bag”, or simply “bag”), which is shown as item 32 in FIG. 4. To remove the opaque lens, an opening (a so-called “capsulotomy”) is made in the anterior part 34 of the capsule 32 manually by a surgeon or by a pulsed laser and the lens 30 is removed through the opening.
To facilitate the removal of the opaque or cloudy lens, the lens is first emulsified by the phacoemulsification method or by a pulsed laser. Phacoemsulification involves making a small incision in the cornea and introducing a very thin needle through the incision, which is then brought into contact with the lens through the capsulotomy. The needle is caused to vibrate at an ultrasonic frequency by the use of a magnetostrictive driver. The ultrasonic vibrations of the needle soften the lens and emulsify it. The emulsified parts can then be aspirated out of the capsule through the incision. Finally, the incision is widened sufficiently to introduce the substitute artificial lens into the capsule. A pulsed laser can be used to create an opening in the capsule, by photoablating capsular tissue along a predetermined boundary, which can be circular or elliptical if desired.
Like the lens of FIG. 2, the lens in the extra-capsular method is conventionally held within the capsule by the use of haptics. One example of this is shown in U.S. Pat. No. 5,376,115. FIGS. 5 and 6 are an extract from this patent, in which the artificial lens 36 with its haptics 38 is introduced through the iris and into the capsule 40 via the capsulotomy (FIG. 5) and finally brought to bear against the inside posterior surface of the capsule (FIG. 6). The haptics 38 are used to center the lens and secure it in place inside the capsule.